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Old 06-26-2010, 09:58 AM
"Robert P. J. Day"
 
Default ubuntu virtualization options when no HW virt support?

i wanted to put together a short document on simple virt options on
ubuntu and wanted to start with what you could do with a simple
32-bit system with no HW virtualization support.

if memory serves, stock qemu doesn't require HW virt support, so i'm
certainly free to use qemu as the "simplest" possible solution. but
these days, ubuntu has taken to bundling qemu with kvm (for acceptable
reasons, i might add). the actual package these days is qemu-kvm, but
checking the page info shows:

"KVM (for Kernel-based Virtual Machine) is a full virtualization
solution for Linux hosts on x86 (32 and 64-bit) hardware.

"KVM is intended for systems where the processor has hardware support
for virtualization, see below for details. All combinations of 32-bit
and 64-bit host and guest systems are supported, except 64-bit guests
on 32-bit hosts.

"KVM requires your system to support hardware virtualization, provided
by AMD's SVM capability or Intel's VT."

so, if i follow this, i can run qemu with no HW virt support, but if
i want to improve qemu's performance with kvm (as most people will
want to do), then *that* requies HW virt support, is that about right?

rday

p.s. i think this is clarified by what i read over at qemu.org:

"When used as a virtualizer, QEMU achieves near native performances by
executing the guest code directly on the host CPU. QEMU supports
virtualization when executing under the Xen hypervisor or using the
KVM kernel module in Linux. When using KVM, QEMU can virtualize x86,
server and embedded PowerPC, and S390 guests."

so qemu itself doesn't need HW virt, but taking advantage of KVM
*would*. i think.

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Old 06-27-2010, 12:18 AM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

On 26 June 2010 10:58, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
> *i wanted to put together a short document on simple virt options on
> ubuntu and wanted to start with what you could do with a simple
> 32-bit system with no HW virtualization support.
>
> *if memory serves, stock qemu doesn't require HW virt support, so i'm
> certainly free to use qemu as the "simplest" possible solution. *but
> these days, ubuntu has taken to bundling qemu with kvm (for acceptable
> reasons, i might add). *the actual package these days is qemu-kvm, but
> checking the page info shows:
>
> "KVM (for Kernel-based Virtual Machine) is a full virtualization
> solution for Linux hosts on x86 (32 and 64-bit) hardware.
>
> "KVM is intended for systems where the processor has hardware support
> for virtualization, see below for details. *All combinations of 32-bit
> and 64-bit host and guest systems are supported, except 64-bit guests
> on 32-bit hosts.
>
> "KVM requires your system to support hardware virtualization, provided
> by AMD's SVM capability or Intel's VT."
>
> *so, if i follow this, i can run qemu with no HW virt support, but if
> i want to improve qemu's performance with kvm (as most people will
> want to do), then *that* requies HW virt support, is that about right?

Not quite.

QEMU is a standalone multi-architecture emulator. It can, amongst
other things, do x86.

KVM is a Linux kernel module which uses Intel VT or AMD-V to offer
x86-on-x86 virtualisation, but it needs the hardware support. It will
not work without.

KVM uses part of QEMU for the UI for creating and managing its VMs.

QEMU is far from the simplest option for VM on Ubuntu, which is
probably VirtualBox. The Free but limited Open Source Edition is in
the repositories but for most users it is probably preferable to
download the full product from www.virtualbox.org

Other freeware options are VMware Player and VMware Server.

For server virtualisation, not consumer desktop virtualisation, there
is Xen and KVM, but both require hardware virtualisation support.


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Old 06-27-2010, 12:43 AM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

2010/6/27 Markus Schönhaber <ubuntu-users@list-post.mks-mail.de>:
> 27.06.2010 02:18, Liam Proven:
>
>> For server virtualisation, not consumer desktop virtualisation, there
>> is Xen and KVM, but both require hardware virtualisation support.
>
> No.
> Xen does require hardware virtualization support to run guests in HVM
> mode. But if one only wants to run paravirtualized guests, it's possible
> to do so on a System/CPU without VT extensions.

True, one can use paravirtualisation without VT or AMD-V, but it's not
much use and only certain FOSS OSs will run within it. These days, for
Xen to have functional parity with other hypervisors, you need
VT/AMD-V.

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Old 06-27-2010, 11:42 AM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

2010/6/27 Markus Schönhaber <ubuntu-users@list-post.mks-mail.de>:
> 27.06.2010 02:43, Liam Proven:
>
>> 2010/6/27 Markus Schönhaber <ubuntu-users@list-post.mks-mail.de>:
>>> 27.06.2010 02:18, Liam Proven:
>>>
>>>> For server virtualisation, not consumer desktop virtualisation, there
>>>> is Xen and KVM, but both require hardware virtualisation support.
>>>
>>> No.
>>> Xen does require hardware virtualization support to run guests in HVM
>>> mode. But if one only wants to run paravirtualized guests, it's possible
>>> to do so on a System/CPU without VT extensions.
>>
>> True, one can use paravirtualisation without VT or AMD-V, but it's not
>> much use
>
> It may not be of much use for you but it's *very* useful for me. And
> neither of us can judge of how much use it may be for others.
>
>> and only certain FOSS OSs will run within it.
>
> Yes, that's basically what paravirtualization is about.
>
>> These days, for
>> Xen to have functional parity with other hypervisors, you need VT/AMD-V.
>
> Maybe. But that doesn't change the fact, that the statement
> "Xen and KVM, but both require hardware virtualisation support"
> is not true.
>
> To explicitly state the difference (again):
> KVM:
> No hardware virtualization -> No KVM whatsoever.
> XEN:
> No hardware virtualization -> PV guests: yes. HV guests: no.

Good for you. You are correct, technically, but trying to explain to
the average user that /certain/ OSs /can/ run under this program on
one type of CPU but on another type of CPU it can run any OS is asking
for trouble.

Bear in mind we are replying to a thread started by an OP who does not
know the difference between QEMU and KVM. I think that in your efforts
to make the answer more technically correct you are muddying the
waters and making said answer less clear, less helpful and less
informative.

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Old 06-27-2010, 11:51 AM
"Robert P. J. Day"
 
Default ubuntu virtualization options when no HW virt support?

On Sun, 27 Jun 2010, Liam Proven wrote:

... snip ...

> Bear in mind we are replying to a thread started by an OP who does
> not know the difference between QEMU and KVM.

since i was the OP, i'd like to defend myself to the extent that
it's not that i don't know the difference between QEMU and KVM, i was
just trying to clarify the current ubuntu packaging scheme such that
there is no simple QEMU package anymore -- it's now qemu-kvm,
suggesting that ubuntu now sees the two as inseparable(?).

and i also wanted to clarify what one could do in terms of
virtualization with, say, stock QEMU, and no HW virt support, that
kind of thing. it's slowly starting to make sense.

rday

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Top-notch, inexpensive online Linux/OSS/kernel courses
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Old 06-27-2010, 12:12 PM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

On 27 June 2010 12:51, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> On Sun, 27 Jun 2010, Liam Proven wrote:
>
> ... snip ...
>
>> Bear in mind we are replying to a thread started by an OP who does
>> not know the difference between QEMU and KVM.
>
> *since i was the OP, i'd like to defend myself to the extent that
> it's not that i don't know the difference between QEMU and KVM, i was
> just trying to clarify the current ubuntu packaging scheme such that
> there is no simple QEMU package anymore -- it's now qemu-kvm,
> suggesting that ubuntu now sees the two as inseparable(?).
>
> *and i also wanted to clarify what one could do in terms of
> virtualization with, say, stock QEMU, and no HW virt support, that
> kind of thing. *it's slowly starting to make sense.

Sorry. No offence meant.

QEMU is not a virtualisation program. It is an emulator; it emulates
ARM and many other platforms on various platforms. Software running
under QEMU is running on a simulated processor and will be much slower
than on native hardware. However, QEMU's emulation of x86 is pretty
quick on x86 as there is a good match between emulated and native
instruction sets, obviously!

There used to be a proprietary kernel module called KQEMU which used
VMware-style trapping of unsafe instructions, combined with native
execution of "safe" code, for near-native performance. In the end I
think this was open-sourced but it's probably still out there
somewhere.

But QEMU has all the code for setting up a VM, managing its resources and so on.

KVM just uses hardware virtualisation to run VMs on x86-64 CPUs with
Intel VT or AMD-V. This is relatively easy, but the programmers needed
a whole set of code to create & manage VMs. They took this code from
QEMU since it was right there & FOSS.

KVM thus needs part of QEMU to work, but it is not related to QEMU.
KVM will only work on CPUs with VT/AMD-V.

Xen works on any x86 but in software alone does not deliver full
virtualisation so OSs need to be modified so as not to use unsafe code
in order to run under it. Such OSs are rare and mainly only FOSS OSs.

However, later, when h/w virt'n appeared, Xen was modified to use
this. With h/w virt'n available, Xen can run any OS in a VM, even
closed-source ones such as Windows.

VMware does pure software virt'n, meaning it can run on any x86. It
scans the code stream for "unsafe" instructions; safe code is run
natively, unsafe code through a s/w interpreter, like QEMU. This was
the product that showed that x86 could be virtualised in defiance of
Popek & Goldberg's rules (q.v.)

It does not use h/w virt'n at all, AFAIK. VMware is closed-source
commercial s/w but there are 2 free versions: VMware Player, for
running VMs from other editions, and VMware Server, which runs on top
of other OSs but is aimed at providing virtual servers. There is also
VMware ESX, ESXi - "bare metal" servers, the latter embeddable into
firmware - and VMware Fusion for the Mac and VMware Workstation for
Windows & Linux.

VirtualBox also uses software virt'n, a different version that coerces
ring 0 code (q.v.) to run in the generally-unused ring 1. User code
runs in ring 2 on x86, I think (q.v.). This does not work on all OSs -
it doesn't work with OS/2, for instance. However, VirtualBox *can* use
h/w virt'n if it finds it. If it can do so it can run OS/2.

VirtualBox was written by a German company called Innovision. Sun
bought it and made it freeware for personal use. There is also a more
limited FOSS version.

Oracle has now bought Sun. So far V'box remains free.

There is also Parallels, a Russian company, but it focuses on Windows
and Mac and does not support Linux hosts, AFAIK.

[Deep breath]

There. Happy now? I didn't really want to write so much but it's a
complicated market.

Summary: if you want to run arbitrary PC OSs under desktop Linux, your
choices are:
- FOSS VirtualBox (free, in Ubuntu repos, limited)
- full Virtualbox (freeware, Ubuntu packages available on website)
- VMware Player (freeware, Ubuntu packages available on website, limited)

Or pay for VMware Workstation.

If you want to virtualise servers, or on a server, and thus don't
really care too much about friendly GUIs, your options are:
- Xen (FOSS - needs h/w virt'n to run arbitrary OS)
- KVM (FOSS - needs h/w virt'n to run at all)
- VMware Server (closed source freeware, needs no h/w virt'n)


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Old 06-27-2010, 01:05 PM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

2010/6/27 Markus Schönhaber <ubuntu-users@list-post.mks-mail.de>:
> 27.06.2010 13:42, Liam Proven:
>
>> Good for you. You are correct, technically, but trying to explain to
>> the average user that /certain/ OSs /can/ run under this program on
>> one type of CPU but on another type of CPU it can run any OS is asking
>> for trouble.
>
> I have no idea why being technically correct wrt a topic which, by
> itself, requires some technical understanding above average, should ask
> for trouble.
>
>> Bear in mind we are replying to a thread started by an OP who does not
>> know the difference between QEMU and KVM. I think that in your efforts
>> to make the answer more technically correct you are muddying the
>> waters and making said answer less clear, less helpful and less
>> informative.
>
> OK, you think so.
> I think it's just the other way round: by omitting information / making
> a statement which is simply not true, you generate confusion.
> Bear in mind, we are not discussing a "how to open a text editor"-level
> topic here.
>
> All in all, you seem to think that you know exactly how much information
> the OP and other readers of this thread can handle, and when they have
> to be "protected" from technically correct information.
> I doubt that you do know that - I surely don't. Therefore I think it's
> better to let them decide for themselves and let them ask for
> clarification if they really do get confused by information.
>
> BTW: Calling KVM a purely server virtualization as you did in your first
> post to this thread is another over-generalization. I, for one, use KVM
> daily as a desktop virtualization and - in combination with libvirt - I
> find creating, running and managing KVM guest to be equally easy as
> with, say, VirtualBox.

[Shrug] OK, fine. Good for you. Have it your own way.

I am happy; I feel I have contributed more, and more useful,
information to this thread than you, but if you want to nit-pick, go
right ahead. I am done.


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Old 06-27-2010, 01:44 PM
Loc Greni
 
Default ubuntu virtualization options when no HW virt support?

2010/6/27 Liam Proven <lproven@gmail.com>:
[snip]
> KVM just uses hardware virtualisation to run VMs on x86-64 CPUs with
> Intel VT or AMD-V. This is relatively easy, but the programmers needed
> a whole set of code to create & manage VMs. They took this code from
> QEMU since it was right there & FOSS.

KVM is independent of x86-64.

[snip]
> Summary: if you want to run arbitrary PC OSs under desktop Linux, your
> choices are:
> *- FOSS VirtualBox (free, in Ubuntu repos, limited)
> *- full Virtualbox (freeware, Ubuntu packages available on website)
> *- VMware Player (freeware, Ubuntu packages available on website, limited)
>
> Or pay for VMware Workstation.
>
> If you want to virtualise servers, or on a server, and thus don't
> really care too much about friendly GUIs, your options are:
> *- Xen (FOSS - needs h/w virt'n to run arbitrary OS)
> *- KVM (FOSS - needs h/w virt'n to run at all)
> *- VMware Server (closed source freeware, needs no h/w virt'n)

Just curious: why do you make KVM a "server" solution ?

Thanks,

Loc

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Old 06-27-2010, 03:12 PM
Liam Proven
 
Default ubuntu virtualization options when no HW virt support?

On 27 June 2010 14:44, Loïc Grenié <loic.grenie@gmail.com> wrote:
> 2010/6/27 Liam Proven <lproven@gmail.com>:
> [snip]
>> KVM just uses hardware virtualisation to run VMs on x86-64 CPUs with
>> Intel VT or AMD-V. This is relatively easy, but the programmers needed
>> a whole set of code to create & manage VMs. They took this code from
>> QEMU since it was right there & FOSS.
>
> * *KVM is independent of x86-64.

Yes, it is, true, but are there any 32-bit only x86 CPUs which have
Intel VT or AMD-V?

> [snip]
>> Summary: if you want to run arbitrary PC OSs under desktop Linux, your
>> choices are:
>> *- FOSS VirtualBox (free, in Ubuntu repos, limited)
>> *- full Virtualbox (freeware, Ubuntu packages available on website)
>> *- VMware Player (freeware, Ubuntu packages available on website, limited)
>>
>> Or pay for VMware Workstation.
>>
>> If you want to virtualise servers, or on a server, and thus don't
>> really care too much about friendly GUIs, your options are:
>> *- Xen (FOSS - needs h/w virt'n to run arbitrary OS)
>> *- KVM (FOSS - needs h/w virt'n to run at all)
>> *- VMware Server (closed source freeware, needs no h/w virt'n)
>
> * *Just curious: why do you make KVM a "server" solution ?

To be honest, I have never even looked at it - I do not own, nor ever
have owned, a PC with a virtualisation-capable CPU. I was under the
impression that it did not have a GUI or anything, nor did it support
features like guest additions, shared mouse pointers or clipboards,
disk or file sharing between guest and host etc.

Given that there are free solutions that do all this, it would seem to
me to be something aimed at places where such functionality is not
important. That is, servers, mainly. That is the only place and role
where I have heard of people running it, as far as I can remember.

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Old 06-28-2010, 12:37 AM
Christopher Chan
 
Default ubuntu virtualization options when no HW virt support?

On Sunday, June 27, 2010 11:12 PM, Liam Proven wrote:
> On 27 June 2010 14:44, Loc Greni<loic.grenie@gmail.com> wrote:
>> 2010/6/27 Liam Proven<lproven@gmail.com>:
>> [snip]
>>> KVM just uses hardware virtualisation to run VMs on x86-64 CPUs with
>>> Intel VT or AMD-V. This is relatively easy, but the programmers needed
>>> a whole set of code to create& manage VMs. They took this code from
>>> QEMU since it was right there& FOSS.
>>
>> KVM is independent of x86-64.
>
> Yes, it is, true, but are there any 32-bit only x86 CPUs which have
> Intel VT or AMD-V?
>
>> [snip]
>>> Summary: if you want to run arbitrary PC OSs under desktop Linux, your
>>> choices are:
>>> - FOSS VirtualBox (free, in Ubuntu repos, limited)
>>> - full Virtualbox (freeware, Ubuntu packages available on website)
>>> - VMware Player (freeware, Ubuntu packages available on website, limited)
>>>
>>> Or pay for VMware Workstation.
>>>
>>> If you want to virtualise servers, or on a server, and thus don't
>>> really care too much about friendly GUIs, your options are:
>>> - Xen (FOSS - needs h/w virt'n to run arbitrary OS)
>>> - KVM (FOSS - needs h/w virt'n to run at all)
>>> - VMware Server (closed source freeware, needs no h/w virt'n)
>>
>> Just curious: why do you make KVM a "server" solution ?
>
> To be honest, I have never even looked at it - I do not own, nor ever
> have owned, a PC with a virtualisation-capable CPU. I was under the
> impression that it did not have a GUI or anything, nor did it support
> features like guest additions, shared mouse pointers or clipboards,
> disk or file sharing between guest and host etc.

KVM is managed by the same tool that is used for xen guests...libvirt
and virt-manager and friends.


>
> Given that there are free solutions that do all this, it would seem to
> me to be something aimed at places where such functionality is not
> important. That is, servers, mainly. That is the only place and role
> where I have heard of people running it, as far as I can remember.
>

I use KVM for Windows XP over here and I have said that on the list
(more than a year ago though) but maybe I am in the minority.

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